﻿using System;
using System.ComponentModel.Composition;

namespace SilverlightCalculator.CalculatorValidationRules
{
    [Export(typeof(ICalculatorValidationRule))]
    public class ValidateValueIsANumber : ICalculatorValidationRule
    {
        public bool IsValid(string value)
        {
            if (!String.IsNullOrEmpty(value))
            {
                int number;
                return int.TryParse(value, out number);
            }
            return true;
        }

        public string ErrorMessage
        {
            get { return "That's not a number"; }
        }
    }
}